Move more things out of FrigateApp (#13897)

* Moved FrigateApp.init_config() into FrigateConfig.load()

* Move frigate config loading into main

* Store PlusApi in FrigateConfig

* Register SIGTERM handler in main

* Ensure logging is setup during config parsing

* Removed pointless try

* Moved config initialization out of FrigateApp

* Made FrigateApp.shm_frame_count into a function

* Removed log calls from signal handlers

python's logging calls are not re-entrant, which caused at least one of
these to deadlock randomly.

* Reopen stdout/err on process fork

This helps avoid deadlocks (https://github.com/python/cpython/issues/91776).

* Make mypy happy

* Whoops. I might have forgotten to save.

Truly an amateur mistake.

* Always call FrigateApp.stop()

frigate/__main__.py

@@ -1,10 +1,16 @@
+import argparse
 import faulthandler
 import logging
+import signal
+import sys
 import threading
 
 from flask import cli
+from pydantic import ValidationError
 
 from frigate.app import FrigateApp
+from frigate.config import FrigateConfig
+from frigate.log import log_thread
 
 
 def main() -> None:
@@ -20,8 +26,50 @@ def main() -> None:
     threading.current_thread().name = "frigate"
     cli.show_server_banner = lambda *x: None
 
+    # Make sure we exit cleanly on SIGTERM.
+    signal.signal(signal.SIGTERM, lambda sig, frame: sys.exit())
+
+    run()
+
+
+@log_thread()
+def run() -> None:
+    # Parse the cli arguments.
+    parser = argparse.ArgumentParser(
+        prog="Frigate",
+        description="An NVR with realtime local object detection for IP cameras.",
+    )
+    parser.add_argument("--validate-config", action="store_true")
+    args = parser.parse_args()
+
+    # Load the configuration.
+    try:
+        config = FrigateConfig.load()
+    except ValidationError as e:
+        print("*************************************************************")
+        print("*************************************************************")
+        print("***    Your config file is not valid!                     ***")
+        print("***    Please check the docs at                           ***")
+        print("***    https://docs.frigate.video/configuration/          ***")
+        print("*************************************************************")
+        print("*************************************************************")
+        print("***    Config Validation Errors                           ***")
+        print("*************************************************************")
+        for error in e.errors():
+            location = ".".join(str(item) for item in error["loc"])
+            print(f"{location}: {error['msg']}")
+        print("*************************************************************")
+        print("***    End Config Validation Errors                       ***")
+        print("*************************************************************")
+        sys.exit(1)
+    if args.validate_config:
+        print("*************************************************************")
+        print("*** Your config file is valid.                            ***")
+        print("*************************************************************")
+        sys.exit(0)
+
     # Run the main application.
-    FrigateApp().start()
+    FrigateApp(config).start()
 
 
 if __name__ == "__main__":